U.S. Pat. No. 6,139,534 to Niedospial, Jr. et al. illustrates and describes a liquid drug transfer device constituted by a vented vial adapter having a longitudinal vial adapter axis and including a top wall with a series of axial directed vent apertures, an annular air filter underlying the series of vent apertures, a downward depending skirt for telescopically receiving a vial therein, a downward depending central dual lumen puncturing spike and an oppositely directed central liquid transfer port. The dual lumen puncturing spike includes a pair of axial directed adjacent lumens, namely, a liquid transfer lumen and a vent lumen. The liquid transfer port is in flow communication with the liquid transfer lumen. The vent apertures are in flow communication with the vent lumen via the air filter. The vented vial adapter includes an elastomeric pre-split septum for maintaining sterility of vial contents. Use of the vented vial adapter may lead to liquid contents inadvertently draining into one or more of the vent apertures or one or more vent apertures being splashed by liquid contents, thereby wetting the underlying air filter to the detriment of its operation.
Liquid drug transfer devices with vented vial adapters are also illustrated and described in inter alia U.S. Pat. No. 4,834,744 to Ritson, U.S. Pat. Nos. 6,503,240, 6,544,246, 6,655,246, 6,997,917 and 7,799,009 also to Niedospial, Jr. et al., U.S. Pat. No. 7,192,423 to Wong, U.S. Pat. No. 7,452,348 to Hasegawa, US Patent Application Publication No. US 2007/0156112 to Walsh, US Patent Application Publication No. US 2008/0172024 to Yow.